The use of microorganisms to treat waste or waste contaminated material is well documented. At the February, 1990, symposium which preceded the "EPA-Industry Meeting on Environmental Applications of Biotechnology" the EPA noted that biotechnology has been successfully utilized to treat soils and sludges from superfund sites which include contaminants from multiple and varied sources. Economic and environmental considerations indicate that bioprocessing technologies offer a significant potential for the remediation and treatment of waste and waste contaminated materials. The use of ultimate disposal technologies such as incineration or chemical fixation and encapsulation results in very large expenditures of capital, in addition to the liability associated with the handling and transport of these materials to the disposal site. Biodegradation methods entail a lower cost relative to most other approaches because they are conducted on site and use less complicated equipment. Furthermore, they can be conducted using a combination of above-ground and in situ treatments for a total treatment approach.
Examples of microbial degradation or treatment of compounds are well known in the art. For instance, U.S. Pat. Nos. 4,843,007 and 4,876,201 disclose the aerobic treatment of polychlorinated biphenyls (PCBs) and acetophenones with Alcaligenes, however, there is no disclosure of aromatic ring cleavage, indicating that the compounds were not degraded to the point of mineralization. Further, U.S. Pat. Nos. 5,009,999 and 4,876,201 disclose aerobic treatment of PCBs with Pseudomonas as well, also with no evidence of ring cleavage. U.S. Pat. No. 4,493,895 discloses the aerobic treatment of halogenated organic compounds with Pseudomonas cepacia, whereas U.S. Pat. No. 5,100,800 discloses treatment of the same compounds with Pseudomonas putida strain UNK-1.
Halo-aliphatic compounds, such as trichloroethylene or dimethylammonium chloride have also been shown to be aerobically degraded. Specific examples are found in U.S. Pat. Nos. 4,713,343 (trichloroethylene), 4,492,756 (dimethylammonium chloride), and 5,079,166 (trichloroethylene).
Funk et al., 1993, Appl. Environ. Microbiol. 59:7, pp. 2171-2177 describes a two-step in situ treatment process for soils contaminated with 2,4,6-trinitrotoluene, hexahydro-1,3,5-trinitro-1,3,5-triazine and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetraazocine. The soil is first flooded with an aqueous buffer and starch to promote bacterial activity. The aerobic heterotrophs in the soil or added as inoculum quickly remove the oxygen from the soil creating anaerobic conditions. Under anaerobiosis the contaminating compounds were partially degraded by the microorganisms. They were, however, not degraded to CO.sub.2 and H.sub.2 O, because only the substituted nitro groups were reduced and the aromatic ring was not cleaved.
Venkataramani and Ahlert, 1984, J. WPCF, 56:11, pp. 1178-1184, disclose the use of acclimated bacteria from a sewage treatment plant to aerobically degrade contaminants in an industrial landfill leachate.
The bulk of the published literature, on biodegradation, is focused on the degradation of single pure chemical by pure cultures and not on the degradation of complex mixtures of organic pollutants by mixed cultures or microbial consortia. Much of the work with pure chemicals also has been conducted at concentrations which are orders of magnitude lower than those commonly encountered with industrial wastes. For example Speitel et al., 1989, Environ. Sci. Technol. 23:68-74) examined the degradation of phenols (e.g. p-nitrophenol, 2,4-dinitrophenol, and pentachlorophenol) using pure chemicals at very low levels, i.e., 1-100 ppb. Similarly, Arcangeli and Arvin, 1992, Appl. Microbiol. Biotechnol. 37:510-517, employed very low toluene concentrations, less than 1 ppm to 6 ppm, in their bioreactor.
In controlled microcosm studies, Heitkamp, et al., 1987, Appl. Environ. Microbiol. 53:129-136), showed that naphthalene, when added to selected soil microcosms at levels of less than 1 ppm could be effectively mineralized within 17 to 31 days.
The degradation of methyl-substituted aromatics, in nature, is generally regarded to occur via the meta-cleavage pathway. However, the degradation of halo-organics, such as, for example, chlorobenzoate, proceeds best through the ortho-cleavage pathway. Knackmuss, (Taeger, et al., 1988, Appl. Microbiol. Biotechnol. 28:603-608; Romanov, et al., 1993, Microbiology 62:887-896) and Pierce (Pierce, et al. 1983, Dev. Ind. Microbiol. 24:499-507; Pierce, et al., 1984, Dev. Ind. Microbiol. 25:597-602), have shown that microorganisms can be enriched which are capable of degrading both methyl- and chloro-aromatics via the ortho-pathway. Likewise, Oltmanns, et al., 1988, Appl. Microbiol. Biotechnol. 28:609-616) have shown that bacteria enriched from nature can be constructed which are capable of degrading 1,4-dichlorobenzene via a modified ortho-pathway, not present in the wild-type strains.
Boronin and coworkers (Boronin et al., 1993, FEMS Microbiol. Letters. 113:303-308) in preparing various naphthalene plasmid constructs in P. putida have shown that when naphthalene is the sole carbon and energy source, the highest specific growth rates are observed with meta-pathway&gt;ortho-pathway&gt;gentisate-pathway.
The degradation of mixed organic substrates, and mixed, substituted aromatics in particular, increases considerably the biochemical complexity of degradation, and the regulatory and physiological control of these degradative processes. A key factor in the degradation of mixed organic substrates, particularly where pathways are inducible, is how the cultures are originally grown (and thus, induced).
Hollander, et al., 1994, Appl. Environ. Microbiol. 60:2330-2338) have noted that Commamonas testosteroni (previously classified as Pseudomonas testosteroni) degrades 4-chlorophenol and 4-methylphenol sequentially and not simultaneously. This degradation occurs via the meta-pathway.
However, where multiple organic compounds were supplied, which were degraded only via the meta-pathway, degradation was simultaneous. Because of the prior induction of the meta-pathway, degradation of compounds which proceed via the ortho-pathway required additional treatment time, because the proper enzymes had to be induced to achieve adequate levels of degradation of these compounds. In such cases, this requirement for increased treatment time has a direct negative impact on treatment economics.
Recently, Grifoll et al., 1994, Appl. Environ. Microbiol. 60:2438-2449) have isolated a Pseudomonas sp. (strain F274) which is capable of metabolizing fluorene, and when grown in the presence of p-hydroxybenzoate, cleaves p-hydroxybenzoate via the ortho-pathway. This strain, however, is incapable of utilizing toluene, naphthalene or benzene.
The same situation was observed by Pettigrew et al., 1991, Appl. Environ. Microbiol. 57:157-162) with the degradation of chlorobenzene and toluene by a Pseudomonas strain, that until the meta-pathway was repressed/modified, the simultaneous degradation of organics metabolized via the meta-pathway and ortho-pathway was not possible.
Viliesid and Lilly, 1992, Enz. Microb. Technol. 14:561-565 have shown that the basal or induced levels of catechol 1,2-dioxygenase (the key enzyme of the ortho-pathway) are directly influenced by the dissolved oxygen tension. Based upon their observations it was necessary for the oxygen tension to be above 4% of saturation (at the initiation of degradation) in order to maintain active ortho-pathway degradation.
In the recent literature, there are examples of cases where higher concentrations (1000 ppm) of phenol, Brown et al., 1993, Critical Review and Case Study on Biotechnology for Pollution Prevention, United States EPA; Hinteragger, et al. 1992 or xylene, Wolfram et al., 1990, NTIS Report No. EGG-M-90407, p.17, in aqueous solutions have been successfully degraded.
However, care should be taken to discriminate between primary metabolism and co-metabolism or resting cell metabolism. See, for example, Spain and Gibson (1988, Appl. Environ. Microbiol. 54:1399-1404), which shows resting cell metabolism of nitrophenols by toluene grown cells; and Taylor and Amador, (1988, Appl. Environ. Microbiol. 54:2342-2344) which shows resting cell metabolism of pyridine by phthalate grown cells.
By definition, heterotrophic bacteria utilize various forms of organic carbon as a source of carbon and energy. In addition to a carbon source, heterotrophic bacteria also require nitrogen and phosphorous for growth. Most commonly, inorganic forms of nitrogen or phosphorous are supplied to meet this requirement, though the use of organic nitrogen in the form of amino acids (amino nitrogen) also have been used historically. While documented in the literature, meeting nitrogen requirements through the use of hydrocarbons which contain nitrogen, e.g., heterocycles or nitrophenol or the use of organic phosphorous compounds e.g., phosphinates is less practiced, Wackett, et al., 1987, J. Bacteriol 169:710-717; Schowanek and Verstraete, 1990, Appl. Environ. Microbiol. 56:895-903. Glyphosate degradation in nature is accomplished by bacteria which not only utilize the organic carbon of this pesticide for growth and energy but utilize the organic phosphorous of glyphosate as the source of phosphorous. In fact, glyphosate degradation in nature is suppressed if other more available forms of inorganic phosphorous are present.
While there is considerable interest in using co-metabolic activity to degrade selected organic wastes, such as TCE, the use of co-metabolic processes to treat mixed wastes is likely to be inefficient, and therefore, ultimately more costly. Klecka and Maier, 1988, Biotechnol. Bioeng. 31:328-335) have shown that when degradable but non-utilizable carbon sources are added to a mixed population of pentachlorophenol degrading bacteria, the rate of pentachlorophenol degradation decreases. When however, utilizable forms of hydrocarbons are added to the mixture, the overall removal rate increases. This increase is due to an increase in biomass which results in overall improvement in degradation.
The aerobic degradation of selected aromatics and polyaromatic hydrocarbons (PAHS) is well documented. However, the aerobic degradation of compounds where present in elastomeric or tarry compositions has never been reported to the knowledge of the present inventor(s). Under conditions of anaerobic respiration (i.e. nitrate reduction/denitrification) the oxidative degradation of these same selected chemicals has been reported, using nitrate as the terminal electron acceptor, Bossert and Young, 1986, Appl. Environ. Microbiol. 52:1117-1122; Bouwer and McCarty, 1983, Appl. Environ. Microbiol., 45:1295-1299. However, the degradation of compounds such as naphthalene is not rapid under nitrate respiration. Mihelcic and Luthy, 1988, Appl. Environ. Microbiol. 54:1188-1198 demonstrated that approximately 63 days were required to degrade naphthalene at a concentration of 1 ppm under denitrifying conditions.
Fries et al., 1994, Appl. Environ. Microbiol., 60:2802-2810, generally indicates that biodegradation of benzene, toluene, ethylbenzene and xylenes under aerobic conditions is well known, although the availability of oxygen due to its low solubility in water and low rate of transport in soils and sediments often becomes rate limiting. Fries describes anaerobic respiration of toluene by microorganisms isolated from nature using .ltoreq.0.5 ppm toluene. The microorganisms could grow on 25 ppm toluene and could be fed 50 ppm toluene. There has been no demonstration that these microorganisms can degrade any higher concentrations of toluene.
Ortega-Calvo and Alexander, 1994, Appl. Environ. Microbiol. 60:2643-2646, have speculated that two physiologically different populations, one free-swimming and the other at the organic interface are involved in the degradation of compounds such as naphthalene (when supplied at concentrations of 0.1-1.0 ppm). From their observations, it appears that the initial activity is conducted by the free-swimming bacteria, which are dependent upon the partitioning of naphthalene to the aqueous phase.
Recently, Hack, et al., 1994, Appl. Microbiol. Biotechnol. 41:495-499 have shown that cells of P. putida when grown on glucose, lost over 50% of this activity within 90 hours when stored at 4.degree. C.
Considerable interest has been raised lately regarding the co-metabolism of trichloroethylene, TCE, by the recombinant strain P. cepacia G4 when grown on toluene. From the recent paper by Landa et al., 1994, Appl. Environ. Microbiol., 60:3368-3374, several conclusions can be drawn. It takes considerable amounts of toluene to degrade a small amount of TCE. Approximately 64 ppm of toluene is required to metabolize 3.2 ppm of TCE (a ratio of 20 parts toluene degraded for each part of TCE degraded). Furthermore, when the TCE concentration exceeds 19 ppm, competitive inhibition of toluene degradation results in the loss of TCE co-metabolism and the cessation of toluene degradation.
Immobilized and entrapped bacterial processes have been established for many years (Atkinson and Movituna, 1991, Biochemical Engineering and Biotechnology Handbook: 2nd Ed. Stockton Press, New York). These processes claim to provide additional benefit with respect to improving the ruggedness of the microorganisms. For example, Dickman, et al., 1990, Bioprocess Eng'r 5:13-17, showed improved stability to oxygen deprivation and pH shocking in an immobilized continuous culture reactor versus free swimming bacteria. Westmeier and Rehm, 1985, Appl. Microbiol. Biotechnol. 22:301-305 have shown that immobilized cells of Alcaligenes sp. degrade 4-chlorophenol at faster rates than do free-swimming cells when fed 4-chlorophenol at low concentrations (i.e., .ltoreq.19 ppm).
Haigler, et al., 1994, Appl. Environ. Microbiol., 60:3466-3469, describes the isolation of a strain of Pseudomonas (strain JS42) based upon its ability to degrade and utilize 2-nitrotoluene (2-NT) as a sole source of carbon, energy, and nitrogen. While this reference shows that this strain was able to utilize 2-nitrotoluene, Haigler specifically states that Pseudomonas strain JS42 is incapable of utilizing nitrobenzene. In addition, Haigler makes no mention regarding the ability to degrade or utilize aniline or naphthalene. While washed cells of strain JS42 grown on 2-NT are capable of oxidizing nitrobenzene, the reference specifically makes clear that the cells cannot utilize nitrobenzene. Therefore, this biotransformation activity is more correctly defined as co-metabolism.
Composting of hazardous organic wastes represents a relatively novel application of biotreatment technology. Most notable is the example of composting of chlorophenols (Valo and Salkinoja-Salonen, 1986, Appl. Environ. Microbiol. 25:68-75). However, the time required to treat contaminated soils using this technology is not rapid (&gt;4 months). Part of the problem with the use of composting for chlorophenols is the development of a significant level of active chlorophenol degraders. While this problem was addressed, in part, by Valo and Salkinoja-Salonen (Id., 1986), through the addition of microbial amendments, this was only possible when the soil had been previously sterilized to kill-off the indigenous microflora.
U.K. Patent No. 1,375,394 states generally that microorganisms of the genera Pseudomonas, Mycobacterium, Flavobacterium or Sarcina can aerobically degrade nitro-aromatic compounds. This reference states that the microorganisms must be induced to have the ability for such degradative activity. However, there is no indication at all regarding what concentration of nitro-aromatic should be used for induction nor any teaching of what culture conditions should be employed. Further, there is no indication in this reference at all regarding what particular species of any of the mentioned genera could be induced to have the desired degradative activity, nor is there any indication where such microorganisms could be found.
European Patent Publication No. 0278296 generally describes a method for the simultaneous chemical and biological treatment of solids and liquids containing organic waste.
Thus, there remains a real need for microorganisms and for systems and processes which are useful for rapid, efficient aerobic degradation of aromatic, nitro-aromatic, halo-aromatic, aliphatic and halo-aliphatic compounds. There is also a real need for degrading any or all of these compounds when present in elastomeric or tarry materials.
Citation or identification of any reference in Section 2 of this application shall not be construed as an admission that such reference is available as prior art to the present invention.